The skeletal dysplasias are a heterogeneous group of disorders which result in disproportionate short stature and/or skeletal deformities. This study involves a multidisciplinary investigation of the clinical, genetic, morphologic, bio-chemical and molecular characteristics of the skeletal dysplasias. The limb lengthening protocol is designed to assess the medical and psychological benefit of experimental limb-lengthening procedures to increase height in individuals with severe short stature.